1. Field of the Invention
The invention relates to a pump with a housing composed of two intersecting cylinder sections, having provided on mutually opposite sides inlet and outlet ports and having in each cylinder section a rotor rotatably disposed about its center longitudinal axis, the major transverse axes of the rotors being positioned approximately perpendicular to each other in at least one movement phase, and the rotors rolling off on one another and against the interior wall of the housing in a sealing manner, the surface lines of each rotor that extend from the intersection of the major transverse axes extending in opposite directions obliquely to the respective center longitudinal axis, and each rotor having two approximately club-shaped sections that are connected to each other at their narrower ends via a waisting, the rotors having a configuration and being disposed relative to each other such that when the major transverse axes of the two rotors are positioned perpendicular to each other, the club-shaped section of one rotor engages into the waisting of the other rotor and the two rotors roll off on one another in a sealing manner, the rotors creating in each phase of the rotation movement an evenly increasing intake volume in front of the inlet port and an evenly decreasing discharge volume in front of the outlet port.
2. Background Art
A pump of this generic type is known from EP 0 363 420 B2.
Such pumps, the generic type of which is assumed to be known, are referred to as Roots pumps or Roots housings and they have proven effective in practice for quite some time.
The rotors of conventional Roots pumps of this type have circumferential surfaces that extend parallel to the center longitudinal axis of the rotor and thus perpendicular to the flow direction that is defined by the inlet and outlet ports. Due to this design of conventional pumps of this type, the pumped medium pulsates relatively strongly in dependence upon the respective rotation angle position of the rotors.
From GB-A-382 953 a pump of the generic type is known in which, however, due to the rotor configuration that is proposed there, an increased pump resistance must be accepted due to occurrences of fluid compression in dead spaces.
From DE-A-35 02 839 a pump with two rotors is known that have two mutually parallel axes of rotation, wherein the sealing surfaces extend obliquely to the axes of rotation in each case. In this prior-art pump the inlet and outlet port are disposed in the axial extension of the axes of rotation. The configuration of the rotors is relatively complicated.
U.S. Pat. No. 1,142,734 describes a pump with two rotors, which, in cross-section, have a club-shaped intermeshing configuration. The outlet and inlet port in this design are disposed on one hand in the region of the front ends and on the other hand on the opposite side approximately in the center of the housing The helical rotors, viewed in the longitudinal direction, are composed of two partial rotors, wherein the curvature of the two partial rotors changes in the region of the perpendicular bisector. The medium that is to be pumped is accordingly pumped substantially in the axial direction from the outsides to the center.